First background almost finished
I've experimented a lot with the perspective, cameras, 3D objects, 2D objects, animations to reach to this point where I'm confident to say: this is how is going to be the game.
Still need details, sounds, ambient, but now I can continue with the next scene.
(actually this is the dull scene, the rest of the game is more like a magical mistery tour)
Here's a video that shows how it moves: